In recent years, a wireless communication function has been mounted on not only information processing devices, such as personal computers, and communication terminal devices, such as cellular phones and PDAs (Personal Digital Assistances), but also various types of consumer electronic devices, such as audio devices, video devices, camera devices, printers, and entertainment robots. In addition, the wireless communication function has been mounted on wireless LAN (Local Area Network) access points and small accessory cards. The accessory cards are wireless card modules having both a storage function and a wireless communication function. Known as wireless card modules are for example PCMCIA (Personal Computer Memory Card International Association) type cards, compact flash cards, mini PCI (Peripheral Component Interconnection) cards.
As the wireless communication function has been mounted on various devices, antennas that receive and transmit radio waves have needed various shapes and characteristics. For example, antennas that can deal with a wide frequency band and multiple frequencies have been needed.
For example, for 5 GHz band used in the wireless LAN, antennas have been needed for 4.9 GHz band and 5.8 GHz band that are wider than the existing 5.15 to 5.35 GHz bands. In addition, to satisfy the IEEE (Institute of Electrical and Electronics Engineers) 802.11a/b/g standards, antennas are needed to cover both the frequency bands 2.4-2.5 GHz and 5.15-5.35 GHz. In an ultra wide band (UWB), which is gaining attention, antennas need to cover wide bands of 3.1 GHz-10.6 GHz. There is a possibility that the UHF bands (400-800 MHz) of ground wave digital broadcasts and high speed wide band milli-wave communication systems (25 GHz band, 60 GHz band, and so forth) will be combined in future.
So far, to cover a plurality of frequencies, the following methods have been proposed: (1) an antenna is designed to have a main resonance and a sub resonance, and (2) an antenna is designed to broaden a frequency band with one resonance. The method (1) of these methods has been widely used in many commercial antennas.
However, these methods have the following problems. The method (1) sacrifices characteristics such as “deterioration of return loss characteristics” “narrow frequency band” in one of a plurality of bands. In contrast, the method (2) sacrifices a gain of a radio wave in a widened band because the band and gain have a reversely proportional relationship.
In an ideal method of widening a frequency band, which has been proposed, a plurality of antenna elements corresponding to necessary frequency bands are mounted on a device (as disclosed in for example Japanese Patent Laid-Open Publication No. 2002-92576).
FIG. 17 shows an example of an antenna substrate having a plurality of antenna patterns. FIG. 17A is a plan view showing one principal surface S3 of an antenna substrate 101. FIG. 17B is a plan view showing another principal surface S4 of the antenna substrate 101. As shown in FIG. 17A and FIG. 17B, the principal surface S3 of the antenna substrate 101 has a first antenna pattern 102a. The other principal surface S4 of the antenna substrate 101 has a second antenna pattern 102b. The first antenna pattern 102a is an antenna pattern corresponding to frequency bands 4.9-5.35 GHz, an antenna pattern corresponding to frequency bands 2.4-2.5 GHz, or an antenna pattern for a DT (Digital Television) corresponding to frequency bands 400-800 MHz. The second antenna pattern 102b is an antenna pattern corresponding to frequency bands 5.35 GHz-5.8 GHz or an antenna pattern corresponding to milli-wave bands.
However, if a plurality of antenna patterns are closely disposed and mounted on a device, they interfere with each other and their characteristics deteriorate. To solve this problem, if a plurality of antenna patterns are disposed with sufficient clearance areas, the size of the device becomes large.
If the antenna substrate 101 shown in FIG. 17 is thinned out (for example, 1 mm or less), the first antenna pattern 102a and the second antenna pattern 102b disposed on both the principal surfaces largely interfere with each other. As a result, characteristics of the antenna deteriorate. Thus, as shown in FIG. 18, the first antenna pattern 102a and the second antenna pattern 102b have to be disposed on the antenna substrate 101 with a sufficient clearance area.
As described above, when a plurality of antenna elements are mounted on a device, the size of the device becomes large. Thus, this method does not satisfy the present needs of which the wireless function is mounted on various consumer devices. Thus, under the existing circumstances, such a method has been hardly used in real devices.
Therefore, an object of the present invention is to provide an antenna apparatus that allows a plurality of antenna patterns to be closely disposed and deterioration of characteristics due to interference of antenna patterns to be suppressed; a wireless apparatus therewith; and an electronic apparatus therewith.